THRESHOLD EFFECTS ON HEAVY QUARK PRODUCTION IN GAMMA-GAMMA-INTERACTIONS

The exchange of gluons between heavy quarks produced in e+e- interactions results in an enhancement of their production near threshold. We study QCD threshold effects in gammagamma collisions. The results are relevant to heavy quark production by beamstrahlung and laser backscattering in future linear collider experiments. Detailed predictions for top-, bottom-, and charm-quark production are presented.

New Higgs couplings at e+e- and hadronic colliders

We examine the potentiality of both CERN LEP and Fermilab Tevatron colliders to establish bounds on new couplings involving the bosonic sector of the standard model. We pay particular attention to the anomalous Higgs interactions with γ, W±, and Z0. A combined exclusion plot for the coefficients of different anomalous operators is presented. The sensitivity that can be achieved at the Next Linear Collider and at the upgraded Tevatron is briefly discussed. ©1999 The American Physical Society.

Three jet events and new strong couplings at LEP and NLC

We study the effects of new dimension-6 operators, resulting from a general SU(3)C ⊗ SU(2)L ⊗ U(1)Y invariant effective Lagrangian, on three jet production at LEP and at the Next Linear Collider. Contributions to the total event rate and to some event shape variables are analysed in order to establish bounds on these operators. © 1999 Elsevier Science B.V. All rights reserved.

New limits on doubly charged bileptons from CERN LEP data and the search at future electron-positron and electron-photon colliders

We show that the accumulated CERN LEP-II data taken at √s = 130-206 GeV can establish more restrictive bounds on doubly charged bilepton couplings and masses than any other experiment so far. We also analyze the discovery potential of a prospective linear collider operating in both e+e- and e γ modes.

New Higgs interactions in ZZ gamma and Z gamma gamma production

The effect of new operators that only modify the bosonic couplings of the Higgs boson, without altering the WW gamma or WWZ three-point functions, are examined in the e(+)e(-) --> ZZ gamma and Z gamma gamma processes. We analyse the constraints on these interactions that can be imposed by the LEP II collider at CERN and at the Next Linear Collider. (C) 1998 Elsevier B.V. B.V.